Effect of Bleaching Agent on Shear Bond Strength to Dentin

Objectives: Tooth bleaching treatment has become increasingly popular. However, side effects of the bleaching treatment has been more pronounced as well. The purpose of this study was to explore the optimal waiting period after tooth whitening treatment to recover bond strength of dentin. Methods: Opalescence F (15% carbamide peroxide) was used as a bleaching agent. For dentin bonding agents, Scotchbond MP and Clearfil SE Bond were utilized. Opalescence F was applied evenly on enamel surface for 4 hours then washed for 30 seconds with deionized water and then stored in clean distilled water for 20 hours daily. This was done for 21 consecutive days. After bleaching treatment, teeth were stored in distilled water for, 1 day, 2 days, 1 week, 2 weeks, and 3 weeks to estimate the effect of wating period. For control, teeth which did not receive any bleaching treatment were selected. Teeth were ground parallel to enamel with SiC paper (#600) to expose dentin and bonding agents were applied and Z100 resin composite was bonded. Shear bond strength of dentin was tested using universal testing machine with 1 mm/min corsshead speed. Each group had 7 samples and results were analyzed with Turkey multiple comparisons test (p=0.05) for statistical significance. Results: Shear bond strengths of samples immediately after treatment and 1 day after treatment were lower than controls (p=0.05). Samples after 2 days and more showed similar streangths with controls (statistically insignificant differences). Scotchbond MP and Clearfil SE Bond showed no sognificant difference on shear bond strength of dentin. Conclusions: Regardless of bonding agents used, after 2 days, samples recovered bond strength to the level before bleaching treatment.